Have made several of JH's actinometers but have always experienced difficulty with the fluid, ammonia sulphate of copper. Can some other fluid be used? They are now making two actinometers for a foreign observatory and would like to make them as accurate as possible.

Asks whether JT can reprint JH's letters on the British modular standard of length, which letters were published in the Athenaeum.

Responds to JH [see JH's 1863-6-2] about basic rules for admission to the observatory [for JH's future guidance]; GA discourages the visit of ladies 'who understand nothing and learn nothing.'

Passes on recent reports of good news that daughter Caroline is improving, and that JH's wife, Margaret, survived the journey well. [Margaret went to Dublin to be with Caroline when she became very ill at the birth of her daughter Kathleen.]